Low melting glass



United States Patent 37/ 57,288 U.S. Cl. 10647 7 Claims Int. Cl. C03c3/12; C03c 5/00 ABSTRACT OF THE DISCLOSURE A glass composition of thePbOB O system in which the softening temperature is lowered by theaddition of T1 0 in the range of from 1 to 65% by weight.

The instant invention relates to glass compositions and moreparticularly to a novel glass composition having a melting pointsubstantially lower than glass compositions presently known in the artand having extremely advantageous characteristics for use as a frit,soldering material, electrical insulating material, lubricating materialand especially as a hermetic seal for semiconductor elements.

In the field concerned with the hermetic sealing of solid-state devices,such as semiconductor elements, glass finds widespread use as thesubstance employed for the hermetic sealing; however, the glasscompositions presently available having conventional melting points werefound to be unsatisfactory and it has therefore become quite importantto find a material which can be used as an adequate hermetic seal andwhich overcomes the disadvantages of conventionally known glasscompositions.

A primary object of the present invention is that of providing the glassin which the softening temperature is lowered substantially. Thesoftening temperature is defined as the temperature in which theviscosity of the glass becomes poises. This is one of the most importantcharacteristics of low melting glass which greatly enhances the scope ofusage of such glass.

It is intended in the instant invention to obtain a glass compositionhaving a low softening temperature and which has a high degree ofstability.

The composition employed is that of a PbOB O system to which is addedthallium oxide, T1 0, the system comprising of PbO and E 0 PbO, B 0 andone or more than one kind of metal oxide.

In accordance with the instant invention, thallium oxide, T1 0, in therange of 165% by weight is added to a PhD-B 0 system, or a PbO B Osystem containing one or more than one kind of metal oxide therein.

It has been found that the above range recited is necessary for thefollowing reasons:

If the percentage amount by Weight of the T1 0 is less than 1%, it hasbeen found that there is no substantial lowering of the softeningtemperature of the glass composition. Also, when the percentage amountby weight of the T1 0 to be added is above 65%, the melting operation ofthe glass composition becomes extremely difficult and a stable glasscannot be obtained resulting in the 3,420,683 Patented Jan. 7, 1969degradation of mechanical strength of the resistivity againstWeathering. It is therefore desirable to limit the percentage amount byweight of added T1 0 to the range of 1-65%.

It is therefore one object of the instant invention to provide a novelglass composition having stability at a melting point which issubstantially lower than glass compositions presently available.

Another object of the instant invention is to provide a novel glasscomposition having an extremely high degree of stability at a meltingpoint level substantially below those of conventional glasscompositions, which novel glass composition is comprised of a thalliumoxide PbO-B O system or a thallium oxide PbOB O system containing one ormore than one kind of metal oxide therein.

Still another object of the instant invention is to provide a novelglass composition having extreme stability at a melting pointsubstantially lower than the conventional glass composition, which novelglass composition is comprised of a thallium oxide PbOB O system or athallium oxide PbOB O system containing one or more than one kind ofmetal oxide therein, in the range of 165% by weight of thallium oxide.

Still another object of the instant invention is to provide a lowmelting glass composition which is comprised of thallium oxide in therange l-% by weight of thallium oxide in a PbOB O system or a PbOB Osystem containing one or more than one kind of metal oxide therein.

These and other objections will become apparent when reading theaccompanying description and tables set forth therein.

Embodiments of the instant invention are described with reference toTables 1-10 set forth herein.

Table 1 shows the softening temperature of the glass versus the amountof T1 0 added to the PbOB O system wherein the proportion of PbOB O isvaried between PbO:B O =8:1 and PbO:B O =3:2 while the percentage byweight addition of T1 0 is varied between 10 and 60%. Table 1 shows theeffect on the softening temperature of the glass of various proportionsof T1 0 added [0 the PbOB203.

Table 2 shows the softening temperature of the glass versus the amountof T1 0 added to the PbOB O system wherein the proportion of the PbO-B Ois held constant throughout while the percentage by weight of T1 0 3 is-varied between and 65 Table 1 clearly shows the contrast of thesoftening temperatures obtained through the addition of T1 0 against thecase where no T1 0 is added to the PbO-B O system.

TABLE 2 Percent Softening temperature PbO B205 T110 C.)

87. 5 12. 5 0 320. 2 84.9 12.1 3 324.3 82.25 11.75 6 322. 7 70.6 11.4 0317. 7 77.0 11.0 12 300. 9 74. 4 10.6 15 296. 2 70. 0 10. 0 277. 4 65.60.4 271.0 r 61. 25 8.75 so 265. 0 10 52.5 7.5 40 257.5 43. 75 6. 25 50241. 4 35.0 5.0 60 230.0 30. 63 4. 37 65 224. 0

. 20 In the case where the T1 0 percentage is zero, the softeningtemperature in C. is 329.2. By an addition of only 3% by weight of T1 0,the softening temperature is lowered to 324.3 C. The softeningtemperature has been found to be lowered to 224.0 C. by an addition of65% 25 by weight of T1 0, which can be seen to be over 31% lower intemperature than the PhD-B 0 system with 0% T1 0 added. Observation ofTable 2 further shows as the percentage amount by weight of T1 0 isincreased from 0-65 the softening temperature in degree centigrade isalso proportionally decreased.

Table 3 shows the softening temperature of the glass versus thecomposition of -PbOB O -Bi O Tl O wherein the amount and proportion ofthe B 0 and Bi O components are held constant.

TABLE 3 Percent Softening temperature PbO B203 B120 T120 C.)

By contrast the percentage additions of T1 0 are given against 0% of T10. With no T1 0 added, the softening temperature is 299.4 C. and withthe addition of T1 0 the softening temperature can be lowered to as lowas 283.5 C. with an addition of only 9% by weight of T1 0. Thus, it canclearly be seen that the softening temperature is lowered as thepercentage content by weight of T1 0 is increased.

Table 4 shows a tabulation of the softening temperature versus theamount of T1 0 added to a PbO--B O -Bi O system in which the proportionof the PbO:B O :Bi O is held constant.

composition versus the amount of T1 0 added to a PbO-B O -Al O systemwherein the proportion of the PbO:B O :Al O is held constant. 75

TABLE 5 Percent Softening temperature PbO B203 A1203 T120 C In contrastwith the glass with 0% by weight of T1 0, lowering of the softeningtemperature is observed in the glass in which T1 0 is added.

Table 6 shows the softening temperature of the glass versus the amountof T1 0 added to a PbOB O -SiO system where the proportion of the PbO:BO :SiO is held constant.

By the addition of T1 0, the softening temperature of the glass islowered distinctly in contrast with the glass having 0% T1 0.

Table 7 shows the softening temperature of the glass versus the amountof T1 0 added to a PbOB O -GeO system where the proportion of the PbO:BO :GeO is constant.

TABLE 7 Percent Softening temperature PbO B20 G602 T160 C In the abovecase, the softening temperature is again lowered with increase of theconstant of T1 0.

Table 8 shows the softening temperature of the glass with the amount ofT1 0 added to a PbO-B O CdO system where the proportion of the PbO:B O:CdO is constant.

TABLE 8 Percent Softening temperature PbO B20: CDO T C.)

In the above case, too, the softening temperature is lowered withincrease of the content of T1 0.

Table 9 shows the softening temperatures of the glass versus the amountof T1 0 added to a PbO-B O TeO system where the proportion of the PbO:BO :TeO is constant.

TABLE 9 Percent Softening temperature PbO B 05 T602 T120 C.)

In this case, also, the softening temperature is lowered with increasein percent content by weight of T1 0.

Table 10 shows the softening temperature of the glass versus the amountof T1 added to the system in which a PbOB O system contains more thanone kind of metal oxide where the mutually relative proportions of thecom- 6 by weight of T1 0 being in the range of 1% to 65%; said PbO, B 0and SiO being contained in the ratio of approximately 11.25 :1:1 byweight.

5. A composition for glass having a low melting point ponents other thanT1 0 are constant. 5 comprising PbO, B 0 GeO and T1 0; the percent TABLEPercent Softening temperature Th0 PbO B203 S10: A1703 ZnO B120: T602 C.)

The above table exhibits the same results as those of the precedingTables 1 through 10.

As is clear from the embodiments of this invention shown in Table 1 to10 the softening temperatures of the glass obtained by the addition ofT1 0 are lower than the glass without T1 0. That is, by the addition ofT1 0 to PbOB O or a PbO--B O system in which one or more than one kindof metal oxides are contained in it is possible to lower the softeningtemperatures of the glass and to provide the glass having the superiorstability.

Although there have been described preferred embodiment of this novelinvention, many variations and modifications will now be apparent tothose skilled in the art. Therefore, this invention is to be limited,not by the specific disclosure herein, but only by the appending claims.

What is claimed is:

1. A composition for glass having a low melting point comprising PbO, B0 and T1 0; the percent amount by Weight of T1 0 being in the range of1%65%; said PbO and B 0 being contained in the ratio of approximately7:1 by weight.

2. A composition for glass having a low melting point comprising PbO, B0 Bi O and T1 0; the percent amount by weight of T1 0 being in the rangeof 1%-65%; PbO, B 0 and Bi O being contained in the ratio ofapproximately 41:6:3 by weight.

3. A composition for glass having a low melting point comprising PbO, B0 A1 0 and T1 0; the percent amount by weight of T1 0 being in the rangeof 1% to 65%; the proportions by weight of PbO, B 0 and A1 0 beingconstant throughout the range of T1 0 added; said PbO, B 0 and A1 0being contained in the ratio of approximately 34:3:3 by weight.

4. A composition for glass having a low melting point comprising PbO, B0 SiO and T1 0; the percent amount amount by weight of T1 0 being in therange of 1% to the proportions by weight of PbO, B 0 and GeO beingconstant throughout the range of T1 0 added; said PbO, B 0 and GeOibeing contained in the ratio of approximately 7.6:1:1:1.175 by weight.

6. A composition for glass having a low melting point comprising PbO, B0 CdO and T1 0; the percent amount by weight of T1 0 being in the rangeof 1% to 65 the proportions by weight of PbO, B 0 and CdO being constantthroughout the range of the T1 0 added; said PbO, B 0 and CdO beingcontained in the ratio of 8:1:1 by weight.

7. A composition for glass having a low melting point comprising PbO, B0 TeO and T1 0; the percent amount by weight of T1 0 being in the rangeof 1% to 65%; the proportions by weight of PbO, B 0 and TeO beingconstant throughout the range of T1 0 added; said PbO, B 0 and TeO beingcontained in the ratio of approximately 16.5 12.5 :1 by weight.

References Cited UNITED STATES PATENTS 3,238,151 3/1966 Kim 252-5183,211,826 10/ 1965 Holcomb et a1. l0649 2,853,393 9/1958 Beck et a1.l0647 OTHER REFERENCES Fajans et al.: Stability of Lead Glasses andPolarization of Ions, J. Am. Cer. Soc., vol. 31 (1948) (pp. 113- 114relied on).

HELEN M. MCCARTHY, Primary Examiner.

U.S. Cl. X.R.

